The present invention relates generally to electrolytic flow cells, and more particularly to electrolytic cells that generate sodium hypochlorite from brine or seawater.
Prior art electrolytic flow cells have a plurality of parallel electrodes that are spaced apart along their outer edges and sealed along their perimeters to form an electrode stack. Electrolyte is admitted through an inlet at the base of the electrode stack and flows in the space between successive adjacent electrodes to an outlet at the top of the electrode stack. The electrolyte passes from one space between electrodes in the electrode stack to the next adjacent space between electrodes through apertures in each electrode. The apertures are horizontally displaced between adjacent electrodes to maximize the length of the flow path over which electrolysis takes place.
The outermost electrodes in the stack are monopolar while the intermediate electrodes are bipolar. Electrical power can then be applied to the electrode stack via electrical connections to the outer monopolar electrodes and this creates an anodic and a cathodic surface on each intermediate bipolar electrode. This causes electrolysis to occur as the electrolyte passes through the cell.
However, these electrolytic cells of the prior art suffer from the disadvantage that the voltage applied to the electrode stack is limited to a threshold value where the material(s) comprising the electrodes themselves begin to undergo electrolysis, limiting the efficiency of the electrolytic cell. Furthermore, passing the electrolyte between a single stack of electrodes results in an electrically charged electrolyte effluent. This electrically charged effluent can present a safety hazard if the electrolyte leaks and contacts a worker. Further, since the effluent is electrically charged, instrumentation valves and associated pipework in the effluent stream before and after the electrolytic cell must be lined or enclosed in or made of a plastic material and sealed against the charge, to prevent accidental contact with or induced corrosion of metallic parts that are in contact with ground potential, thereby increasing the complexity and cost of the cell's associated instrumentation pipework and fittings. The effects of stray current corrosion on the inlet pipework and instruments can be greater than on the outlet as the cell's positive power connection, i.e., the highest potential, is at the inlet to the cell.